Just to follow up on my last post, I wanted to provide some additional information and the actual flight data, and briefly explain what this all means, especially for all those folks reading this who are not familiar with anything related to rockets or flight computers. And for anyone who has significant experience flying rockets, you may find the below information interesting as well, without any explanation!
As a starting point: a flight computer is basically a very small circuit board that you put inside your rocket, and it has a bunch of neat built-in gadgets to measure exactly how high the rocket went, and how fast, and what interesting events happened when. I’ll explain more below.
This is the relevant flight data for the flight I mentioned in my last post, which went over one mile high:
So what does all of this mean?
First of all, it means that the rocket flew to a maximum height of about 7,579 ft – you can see this in “maximum height.” This measurement is made by a barometer taking air pressure readings in the flight computer, starting at ground level on the launch pad, and then many times while it’s in flight. There’s also a GPS chip on this flight computer and you can see it also independently measures the height using GPS, but I’m just going to assume the lower value is more likely correct.
The flight computer also records the maximum speed, which in this case was 904 feet per second (fps), which is equivalent to Mach 0.8, or a little bit slower than the speed of sound.
The total flight time was 145 seconds (just over two minutes), and there’s a further breakdown of how long the rocket spent going up and then coming back down.
The graph is even more intuitive:
This reflects the same data described above. The black line is the easiest to understand: it represents the rocket’s actual height over time. As is generally the case (unless you experience a catastrophic failure), the rocket zooms off the launch pad extremely rapidly and hits a maximum height early (here, just over 7,500 ft, as you can see from the black units to the left side), and then after parachutes deploy, it descends more slowly.
The red line is speed (extremely high at first and then plummets quickly), and the orange or gold line is acceleration. Both of these units are off to the right side of the graph.
It’s definitely fun to build and fly a rocket, but with modern flight computers and the ability to record all kinds of really precise data, you can really geek out on this stuff. How high can I fly? How fast can my rocket go? Is it descending at the right speed, or do I need a bigger (or smaller) parachute next time? This can really help refine your building and flying skills through a trial and error process, because you have access to reliable data. And needless to say, this can also help you find your rocket if you lose it because it lands really far away out of sight. In that situation, you’ll find the GPS coordinates onboard to be incredibly useful!
The National Association of Rocketry (“NAR”) has established a “Rocket Science Achievement Award” program, which currently has three categories of awards:
- Mile Marker
- Faster Than Sound, and
- Data Downlink.
The awards are pretty straightforward: to achieve Mile Marker, you need to fly a rocket to at least 1 mile (5,280 ft), and you can get additional awards for 2 or 3 miles, or as many as you’d like, in one-mile increments. To achieve Faster Than Sound, you just have to fly a rocket at a speed that is Mach 1.0 or higher. And the Data Downlink award involves real-time telemetry for data beyond just basic altitude and acceleration.
For any of these awards, you have to have documentation of the flight data, including a copy of the data file from a commercial flight computer. If you submit this documentation and it’s accepted, you’ll be awarded a high quality printed certificate and your name will be added to the NAR website, which is pretty cool.
I recently achieved the Mile Marker award when I flew my Darkstar Extreme rocket to 7,579 ft AGL. I plan on even higher flights in the future, of course, and I’d like to try to achieve an award in each of the three categories that NAR established. The data downlink one should be the most interesting and will require a bit of creativity.
In case you’re interested, the award page is here!
I gave a brief preview in a recent post, but I’m excited to report that the L3 Fusion rocket is now finished. This is a kit available for pre-order from Scott Binder at SBR, and I was fortunate enough to partner with Scott to do a test build on his latest design.
As mentioned a while back, the L3 Fusion is a larger, upscaled version of his classic Fusion rocket. It has a 5.5″ diameter airframe and is about 90 inches in length, with a 75mm motor mount tube capable of flying on an M motor. What’s particularly great about this rocket is that it combines strength with being lightweight. Its cardboard airframe weighs in at just 11 lbs when fully loaded, minus the motor.
And yet it’s fully double-tubed from top to bottom, and the entire interior is coated with West System epoxy to harden and strengthen it. This thing can take a beating, and it is more than strong enough to handle an M motor.
I plan to fly it for L3 certification on an Aerotech M-1297 motor. Believe it or not, this will be my first time using a reloadable (RMS) motor, and my first time putting one together. I’ve previously just used disposable (DMS) motors since they’re so easy to handle – minimal preparation, and then discard entirely after the single use. But having now built the M-1297 in preparing to fly, I have to admit there’s something satisfying about putting together the motor yourself. Of course, it’s a bit messy and you’ll get your hands dirty – and the casing is not cheap – but the end product speaks for itself.
In addition to building the rocket, we also set up a small studio and filmed the entire project, from start to finish. Throughout the process, I try to explain what I’m doing, though I’m far from an expert (I am, after all, just applying for my L3 certification). It was a lot to film, and as you can imagine, the video editing process is extremely time-consuming (props to Scott for undertaking this). But it should make for a great tutorial on YouTube, and I’ll post the video as soon as it’s ready!
You may have noticed a few recent changes to the website, and there are more in the works. I just thought I’d take a moment to explain some of the things that I’ve been doing.
First, the website now has a new domain, “improbableventures.org,” instead of the original wordpress domain, “improbableventures.home.blog.” Either one will work and you’ll be directed to the same website, but getting a custom domain was the appropriate next step.
Similarly, we created a banner for the website last year, and it’s gone through several iterations. We’re still playing around with it and are looking forward to unveiling a new logo soon, as well.
And on that note, you may ask: who is “we”? Improbable Ventures is growing, with two new members of the team. We’ll roll out a more formal announcement with additional info soon, but wanted to give everyone a preview of where Improbable Ventures is headed, and what we’ll be doing in the near future! Our team will be:
- Posting more YouTube videos to our channel, detailing high power rocket construction;
- Designing and building a high-altitude two-stage rocket, capable of flying to 100,000 ft;
- Developing our own flight computer;
- Machining aluminum parts, and building an all-aluminum rocket;
- Designing and testing a liquid fuel rocket engine;
And some additional top secret projects to be announced later!
My previous high power rocket builds have been relatively slow. Don’t get me wrong – I generally don’t procrastinate, and once I get excited about a rocket project, I dive in and don’t come up for air until it’s complete.
But my techniques are far from perfectly efficient, and there’s often a substantial amount of long-curing epoxy, and then waiting for it to cure. And then… repeat. Each cure takes hours or even needs to wait overnight, and I’m doubly and triply reinforcing everything to make sure it’s sufficiently strong. Plus I’ve only built a few larger high power rockets so far and I was inevitably much slower in the beginning.
With this L3 Fusion build, however, I was able to move at a much more rapid pace. One big reason was using a fast-curing 12 minute epoxy. You just mix the resin and hardener and get to work. With a 12 minute cure, it’s amazing how quickly you can build!
That being said, for purposes of filming every step, this was still a marathon build session. It took a couple days of nonstop construction, even though the steps themselves are pretty simple and there was nothing that I hadn’t done before. At least, in principle. The “marathon” aspect was only because of filming and trying to make the most efficient use of our time.
We did have a few minor technical difficulties. Despite an excellent studio setup with a camera and tripod, external microphone, bright lights, and so on, there were several long stretches where we captured excellent video but the audio was completely missing. This meant we had to go back and figure out what went wrong with the microphone (troubleshooting this was much more difficult than you might think) and then re-shoot some of the steps. This turned out to have a silver lining, though, because the second time through I was substantially less inept than my initial attempts. Still inept, that is, but less so.
All in all, this was a really cool project, an awesome rocket build, and a successful video shoot. As soon as we’re done with the editing and have a final product, SBR will share the video on its YouTube channel (and I’ll share it as well, on my channel). In the meantime, if you’re looking to embark on your L3 certification, I highly recommend that you consider this L3 Fusion rocket!
Once I completed my level 2 certification, I had been spending a lot of time thinking about what, exactly, I should build for my level 3 project. And more generally, how should I approach it?
Cardboard or fiberglass?
I’ve built both cardboard and fiberglass rockets, and each has advantages depending on what you’re trying to achieve. I had initially assumed any L3 project would need to be fiberglass, and I’d been looking at some very large and very heavy rockets.
Fiberglass is more durable than cardboard, and is the strongest building material aside from metal. It won’t change size based on fluctuations in temperature, and it won’t swell up or get ruined if wet. This is particularly important since the rocket parts need to slide over each other using couplers. But the primary drawback of fiberglass is that it’s really heavy.
Cardboard (especially when properly reinforced with epoxy) is still durable but more lightweight, and that is a key characteristic when you are trying to defy gravity and launch something into the air. A cardboard rocket will go a lot higher than a fiberglass rocket on the same motor.
While agonizing over this fundamental choice, a solution appeared, from out of nowhere.
Deus ex machina
I had previously met and worked with Scott Binder, the owner of Scott Binder Rocketry (“SBR”), creator of the Fusion Rocket, as well as high power rocket motors and accessories. Scott’s shop is located in Walla Walla, Washington. His flagship rocket is the Fusion, but he’s recently been developing a new, larger version of the Fusion that is specifically for L3 certification – and long story short, I agreed to do some beta testing on this rocket.
In addition to building the rocket and using it for my L3 cert, I am going to create a video tutorial with Scott for the construction of this rocket, from start to finish. I’ll link to that as soon as it’s ready.
The L3 Fusion itself is roughly 90 inches in length and a 5.5 inch diameter. With a 75mm motor mount tube, it’s capable of flying an M motor, and I plan to fly it on an Aerotech M1297 for the cert flight. The great part about cardboard is that this rocket only weighs about 22 lbs fully loaded, and it should come close to 10,000 ft. at apogee on the M1297.
The electronics bay will have two RRC3 altimeters, each powered by a 9V battery, and will use omni-directional black powder charges for separation and deployment of the parachutes during flight. The drogue chute is 24 inches and the main chute is 84 in. Descent should be less than 20 feet per second under the main chute.
There are more details forthcoming, but right now I’m excited to dive into this L3 project! I need to begin putting together a comprehensive document describing the rocket, with a lot of technical information. Later, once I begin building, I’ll include a lot of detail about the construction process and materials, with plenty of photos documenting the build step by step. And much later, once it’s complete, the most exciting part: flight!
More to come soon!
Recently, I was able to make the journey out to Brothers, OR to attend my first launch hosted by the Oregon Rocketry Club (“OROC”). From where I live in the Seattle area, this is about a 6.5 hour drive each way, so I stayed overnight in Portland. I’ve done some pretty long day trips, but trying to drive to this launch and back in a single day would just be pushing myself a bit too far.
I really only spent half a day at the launch, but it was absolutely worth the trip. I was able to launch two rockets – the cardboard HyperLOC 835 that I used for my L1 and L2 cert, and also the fiberglass Darkstar Extreme. This was the maiden flight for the latter rocket and it did not disappoint.
More importantly, this was my first chance to attend a large launch event with a lot of other people (although of course due to COVID-19, attendance was more limited than normal, and attendees were required to follow a variety of safety precautions, including wearing masks and spreading out). I got to witness lots of other flights, which was amazing, and I met some great people.
To summarize the launch site and conditions, it was hot, dry, and dusty. The winds periodically picked up, too, which made the dust more of an issue. But overall, coming from Seattle, I think this was an excellent place to launch.
I flew the HyperLOC 835 here on an I-500 motor just for fun. It was a successful flight, but the wind gusts were pretty high at times. After the parachute deployed, the winds carried the rocket far from the range. I saw where it landed (or so I thought) and began walking in that direction. Once the rocket touches the ground, though, it completely disappears behind the sage, so you have to just hope you’re still walking in the right direction. The longer you walk, the more your confidence begins to waver, and eventually it melts away as the uncertainty increases in direction proportion.
As it turns out, I apparently overshot it and went significantly further than I needed to. I walked for what felt like an eternity, eventually gave up and headed back toward the range – and then fortunately spotted the rocket hiding behind a bush.
The main event for me, however, was the chance to fly the newly completed Darkstar Extreme, my first fiberglass rocket. This one weighs about 14 lbs and is overall a much more durable rocket. I had some assistance in getting it up on the launch pad.
I have to confess: I was a bit nervous because it was the first flight for this rocket. Sure, I’d built it and done some ground testing at home in my back yard, but was that sufficient? Would everything still work? The really critical components are related to the electronics for dual deployment of the parachutes. If the rocket never separates in the air and the parachutes don’t deploy, then this thing is coming back down like a ballistic missile. Not ideal for the rocket or for all the bystanders.
I was particularly concerned about whether I’d used enough black powder in the e-bay. When it detonated, would it be with enough force to separate the rocket? I’d done some ground testing at home and it separated, but not with the level of force I would like, and I hadn’t had time to do additional testing.
As I feared, the black powder exploded but not with enough force, and it didn’t cause separation. Fortunately, the motor ejection charge detonated as planned and this did cause the rocket to separate, so at least the drogue (smaller) parachute deployed. The heavy rocket came down a bit fast under such a small parachute – roughly 55 feet per second – but this was within a tolerable range and the rocket didn’t sustain any damage whatsoever. I count myself lucky.
Incidentally, the Darkstar Extreme flew on a K-535 motor and hit about 3,500 ft in altitude.
These launch experiences are a tremendous learning opportunity for me. Each time I attend one, I learn a lot, and in particular from my mistakes. Now I realize firsthand how important it is to properly calculate, measure, and test the correct amount of black powder to use for separation charges – and to test, and test again.
In addition, this experience underscored how critical it is to have a backup plan. After this launch, I decided to go back to the workbench and completely rebuild my e-bay for the Darkstar Extreme. I would add a second (backup) flight computer, along with a second battery and power switch, additional wiring and BP charge holders, and so on. Given the difficulty of locating a rocket after it lands, I also decided to add a sonic beeper just to help reduce to chances of losing a rocket. It would be easy to walk right by your rocket just a few feet away behind some bushes, and never even realize it – but a noise making device would alleviate that problem.
Nobody said that this would be an easy journey, but it’s definitely enjoyable and rewarding. Can’t wait for the next launch!